In ΔABC, D is a point on BC such that ∠ADB = 2∠DAC, ∠BAC = 70° and ∠B = 56°. What is the measure of ∠ADC?
In ΔABC, D is a point on BC such that ∠ADB = 2∠DAC, ∠BAC = 70° and ∠B = 56°. What is the measure of ∠ADC? Correct Answer 72°
Given:
In ΔABC, D is a point on BC
∠ADB = 2∠DAC
∠BAC = 70° and ∠B = 56°
Concept Used:
linear pair of angles
Sum of linear pair of angles = 180°
Sum of angles of triangle = 180°
Calculation:
[ alt="F1 Madhuri Teaching 11.05.2022 D1" src="//storage.googleapis.com/tb-img/production/22/05/F1_Madhuri_Teaching_11.05.2022_D1.png" style="height: 166px; width: 216px;">
Let ∠BAC = x°
So, ∠ADB = 2x°
Since, ∠BAC = 70°
So, ∠BAD = (70 - x°)
Now, In ΔABD
56° + 2x° + 70 - x° = 180°
⇒ x = 54°
⇒ 2x = 108°
Now, By linear pair of angles
∠ADB + ∠ADC = 180°
⇒ 2x + ∠ADC = 180°
⇒ 108° + ∠ADC = 180°
⇒ ∠ADC = 180° - 108°
⇒ ∠ADC = 72°
∴ The required measurement of angle is 72°.